I can't figure out how to make PNG file with UV map
First, you should try the latest version of blender (2.81 at the moment), then just go the the UV menu (in the UV Editor) and select "Export UV Layout" : you 'll be asked to choose a file name, image type AND a resolution so you can paint on it in an external paint program. 


But If you want, you can also just go the Texture Paint mode, create an empty texture Map and directly paint on your model ! Have Fun !